This invention relates generally to the detection of fluid leaks and more particularly to a method and device for detecting leaks in hydraulic directional control valves and the loads which they control.
Directional control valves are widely used to regulate the fluid flow to and from hydraulically powered machinery such as power cylinders, hydraulic motors, hydraulic presses and the like. After extensive use, the valves become worn and develop internal leaks which add significantly to the power requirements of the hydraulic system. Moreover, if such leaks go undetected, they eventually cause the valve to fail completely such that the machine must be shut down for emergency repairs at a possibly inopportune time. Accordingly, it is desirable for the valves to be inspected periodically, as during routine maintenance checks.
At present, however, the detection of leaks in directional control valves is a difficult and time-consuming task which is carried out most commonly by checking them on a test stand. The use of a test stand requires that the valves be completely removed from the hydraulic circuit in which they are included. Usually, electrical disconnections must be made in addition to the mechanical disconnections since most valves are operated electrically. The testing is then carried out and the valve is reinstalled in its operating position. As can be appreciated, the procedure involved in using the test stand is so complicated that it is not practical to check the valves as often as would be desirable.
Furthermore, the test stands are costly items and their accuracy is often lacking, primarily because it is nearly impossible to duplicate for testing purposes the conditions under which the valve actually operates. For example, if the valve is tested at a pressure greater than that encountered during normal operation and is found to leak excessively, it still may function adequately under its normal low pressure conditions. Thus the test may be invalid. Conversely, if the valve is tested at low pressure and found not to leak significantly, the test may again be invalid because the valve may leak excessively if its normal use is in a high pressure line. Other possible variations (such as in flow rate or temperature) between the test conditions and the actual operating conditions increase the likelihood of obtaining invalid results from the conventional testing procedure.
A similar problem is encountered with respect to fluid leakage from the loads which are controlled by hydraulic directional control valves. As an example, if a hydraulic motor or cylinder should leak, the power requirements of the system are substantially increased and the machine will eventually fail to operate properly. Accordingly, it is desirable to periodically check for leakage in the load as well as in the valve.
It is the primary goal of the present invention to meet the need for a simple and economical method of checking for fluid leakage, both in hydraulic directional control valves and loads under their actual operating conditions.
Another object of the invention is to provide a leak detection device of the character described in which the leaking fluid creates a pressure differential that is used to indicate the rate of leakage.
Still another object of the invention is to provide a device of the character described which utilizes the pressure differential to retract an indicator member in proportion to the leakage rate.
A further object of the invention is to provide a device of the character described wherein the indicator is a stepped member that can be felt with the fingers in order to determine the extent of its retraction in situations where visual observation is difficult or impossible.
An additional object of the invention is to provide a device of the character described that includes interchangeable orificed members which present orifices or varying effective size. Accordingly, the pressure differential caused by the leaking fluid can be made to correspond with the maximum leakage rate that is deemed acceptable for the particular hydraulic circuit and equipment involved.
Yet another object of the invention is to provide a device of the character described which includes means for preventing excessive pressure buildup, as when a large leak is present in the valve or load.
A still further object of the invention is to provide a leak detection method which can be carried out quickly and accurately.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.